This invention is directed to a low friction pivot, particularly a pivot which has no sliding motion and thus does not require lubrication.
Pivot structures are well known, and most machinery requires the rotation of one member with respect to another. Bearings are highly developed in the art, and the most common bearing structure is where a cylindrical pin rotates within a corresponding bearing surface. Lubrication is required in the ordinary installation, and where high rotative speeds are achieved there is no metal to metal contact because of the hydrodynamic forces which separate the relatively moving parts. In order to overcome the relative sliding motion, antifriction bearings have been developed. These antifriction bearings have balls therein running in races, or have cylindrical or conical rollers therein operating between races. Since there is a small amount of rubbing in such bearings, due to deflections under load, lubrication is required to obtain a reasonable life. Lubrication produces problems, particularly in installations which are intended to operate at temperature extremes. At very low temperatures, the hydrocarbon type of oil and grease becomes hard. At very high temperatures, such lubricants vaporize. Specialized lubricants have been developed to extend the temperature operating range of such bearings, but such do not satisfy all the requirements. Some installations operate in vacuum, and such absence of atmospheric pressure gives further rise to lubrication difficulties. However, where continuous rotation is required, the installation must be designed so that those problems are not overwhelming. Such rotating shaft structures also have the problem of rotating friction. At high speeds, hydrodynamic lubrication eliminates metal to metal rubbing contact and thus the drag problems and mostly related to the shear in the lubricant. However, in slowly rotating pivots the starting drag can seriously hinder linearity of motion.
In rotating structures where very limited rotation is required, the bending of a structure can be employed to permit the rotation. Examples of such a structure are found in the following U.S. Pat. Nos. Re 30,290; ;3,288,541; 3,384,424; 3,575,475; 3,597,938; 4,700,289 and 3,811,172. These patents are rather accumulative in their teaching and teach that very limited rotational motion of one member with respect to another may be accomplished by the bending of metal. One particular teaching of each of these patents is that the webs in bending all operate in the same rotary direction and apply a resilient restoring force toward the zero, non-flexure postion. Thus, the employment of such structures is limited to uses wherein the angular rotation is very small and wherein a large restoring force can be tolerated.